U.S. patent number 4,651,580 [Application Number 06/759,318] was granted by the patent office on 1987-03-24 for actuators.
This patent grant is currently assigned to AE PLC. Invention is credited to Norman P. Deane.
United States Patent |
4,651,580 |
Deane |
March 24, 1987 |
Actuators
Abstract
An electric motor driven actuator comprises an electric motor
whose rotation causes rotation of a planet carrier carrying planet
gears which engage an annulus gear on the inside of a stationary
ring. A pinion transmits rotation of the planet carrier to further
planet gears which are carried on another planet carrier and engage
another annulus inside an axially movable ring. This ring can be
moved axially by an armature in dependence on energization of an
electro magnetic coil within a housing. When the ring moves towards
the first-mentioned, stationary, ring, face teeth which it carries
engage face teeth on the latter ring, and the axially movable ring
is thus held stationary. Its planet carrier thus rotates and a
coupling rotates a shaft which, via a tape, transmits drive to an
output cable. When the coil is de-energized rings, separate again
and the axially movable ring is no longer held stationary and its
planet carrier no longer rotates.
Inventors: |
Deane; Norman P. (Rugby,
GB2) |
Assignee: |
AE PLC (Warwickshire,
GB2)
|
Family
ID: |
10564572 |
Appl.
No.: |
06/759,318 |
Filed: |
July 26, 1985 |
Foreign Application Priority Data
|
|
|
|
|
Jul 27, 1984 [GB] |
|
|
8419238 |
|
Current U.S.
Class: |
74/89.2; 475/299;
475/154 |
Current CPC
Class: |
B60K
31/02 (20130101); F02D 11/10 (20130101); H02K
7/06 (20130101); F02D 2011/103 (20130101); Y10T
74/18832 (20150115) |
Current International
Class: |
B60K
31/02 (20060101); F02D 11/10 (20060101); H02K
7/06 (20060101); F16H 019/02 (); F16H 001/46 () |
Field of
Search: |
;74/89.2,768,785,788 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0030022 |
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Jun 1981 |
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EP |
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0110421 |
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Jun 1984 |
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EP |
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855785 |
|
Jul 1949 |
|
DE |
|
7821020 |
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Dec 1979 |
|
DE |
|
3145217 |
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May 1983 |
|
DE |
|
590050 |
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Jun 1925 |
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FR |
|
59-89855 |
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May 1984 |
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JP |
|
685972 |
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Jan 1951 |
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GB |
|
1058593 |
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May 1964 |
|
GB |
|
1039195 |
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Aug 1964 |
|
GB |
|
1207754 |
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May 1968 |
|
GB |
|
1265510 |
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Dec 1969 |
|
GB |
|
1531355 |
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Jul 1976 |
|
GB |
|
1532044 |
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Aug 1976 |
|
GB |
|
2141203A |
|
Dec 1984 |
|
GB |
|
2157387A |
|
Oct 1985 |
|
GB |
|
Primary Examiner: Staab; Lawrence
Attorney, Agent or Firm: Leydig, Voit & Mayer
Claims
What is claimed is:
1. An actuator, comprising
a motor having a rotatable output shaft,
an output member mounted for translational movement, epicyclic
gearing for providing geared reduction of the rotation of the motor
shaft and connecting it to the output member to cause translational
movement thereof, the epicyclic gearing being arranged axially of
the motor shaft and comprising two epicyclic gear units,
one said epicyclic gear unit being in the form of a plurality of
planet gears supported on a planet carrier and engaging an annulus
gear, the planet gears when rotated being arranged to cause
rotation of the planet carrier when the said annulus is held
stationary,
the other said epicyclic gear unit being arranged coaxially with
the said one epicyclic gear unit and being in the form of a further
plurality of planet gears supported on a further planet carrier and
engaging a further annulus gear, the planet gears of the said other
epicyclic unit being connected to be rotated by the motor output
shaft and the planet carrier thereof being connected to rotate the
planet gears of the said one epicyclic unit, the annulus of the
said other epicyclic unit being held permanently stationary,
and
a clutch for interrupting the drive between the motor output shaft
and the output member, the clutch comprising means for releasably
braking the annulus of the said one epicyclic gear unit,
the said annuli carrying respective arrays of teeth which face each
other axially, and the said means for releasably braking the
annulus of the said one epicyclic gear unit comprising means for
moving the annulus of the said one epicyclic gear unit axially so
as to bring its teeth into and out of engagement with the teeth on
the annulus of the said other unit.
2. An actuator according to claim 1, in which the clutch includes
an electromagnetically energisable coil and an armature which moves
in response to energisation of the coil and causes axial movement
of the annulus of the said one epicyclic unit.
3. An actuator according to claim 1, in which the motor is an
electric motor.
4. An actuator according to claim 1, in which the actuator output
member is a cable.
5. An electric motor-driven actuator, comprising:
an electric motor;
a first epicyclic gear unit having a stationary annulus gear
mounted coaxially of the motor shaft, and a planet cluster
comprising a plurality of planet gears rotatably supported on a
planet carrier and internally meshing with the annulus gear and
connected to be rotated by the motor shaft so as to cause the
planet carrier to rotate;
a second epicyclic gear unit comprising a second annulus gear
mounted coaxially of the motor shaft and a second planet cluster
comprising a plurality of planet gears rotatably supported on a
planet carrier and internally meshing with the second annulus and
connected to be rotated by rotation of the planet carrier of the
first epicyclic unit;
clutch means for releasably braking the annulus of the second
epicyclic unit so that, when the second annulus is braked, rotation
of the motor shaft causes rotation of the second planet carrier
and, when the second annulus is not braked, rotation of the motor
shaft results in rotation of the annulus of the second unit but not
in rotation of the planet carrier thereof;
the annulus gears being in the form of cylindrically shaped rings
which also carry respective arrays of teeth facing each other in an
axial direction, and the clutch means comprises thrust means for
moving the ring forming the annulus of the second epicyclic unit
towards and away from the other ring in an axial direction so as to
move the said teeth into and out of engagement with each other;
and
a coupling connecting the planet carrier of the second epicyclic
unit to cause translational movement of an actuator output member
of the actuator.
6. An actuator according to claim 5, in which
the said coupling comprises an output shaft connected to be rotated
by the rotation of the planet carrier of the second epicyclic unit
and mounted coaxially of the motor shaft, and
the actuator output member comprises a cable mounted substantially
normal to the axis of the output shaft, and drive means converting
rotation of the output shaft into linear movement of the cable.
7. An actuator according to claim 6, in which the drive means is in
the form of a spiral tape arranged concentrically of the output
shaft with one end linked to the output shaft and the other end
linked to the end of the cable.
8. An actuator according to claim 6, in which the drive means
includes gearing for increasing the mechanical advantage between
the output shaft and the linear movement of the cable.
9. An actuator according to claim 6, in which the drive means
includes limiting means for limiting the total angular movement of
the output shaft, the limiting means comprising a rotary member
carried by the output shaft and rotatable adjacent to a fixed
member, a spirally arranged groove in one of the said members and
pin means engaging the groove and carried by the other of the
members, whereby the said angular movement is limited by the length
of the groove.
10. An actuator according to claim 5, in which the thrust means
comprises an electrically energisable coil and an armature
responsive to the electromagnetic force produced thereby.
11. An actuator, comprising
a motor having a rotatable output shaft,
an output member mounted for translational movement,
first and second epicyclic gear units mounted coaxially of each
other and of the output shaft and each being in the form of a
plurality of planet gears supported on a planet carrier and
engaging an annulus gear,
the first epicyclic unit providing geared reduction of the rotation
of the output shaft and connecting it to the second epicyclic unit
which provides further geared reduction and is connected to the
output member to cause corresponding translational movement
thereof, and
a clutch for interrupting the drive between the motor output shaft
and the output member and comprising means for releasably braking
the annulus of one said epicyclic gear unit,
the annulus of the second epicyclic unit being held permanently
stationary and the said annuli carrying respective arrays of teeth
which face each other in the axial direction,
the said clutch comprising means for releasably braking the annulus
of the said first gear unit by moving the annulus in the axial
direction so as to bring its teeth into and out of engagement with
the teeth on the annulus of the said second gear unit.
12. An actuator according to claim 11, in which the clutch includes
electromagnetic means for moving the annulus of the first gear unit
axially.
Description
BACKGROUND OF THE INVENTION
The invention relates to actuators. Actuators embodying the
invention and to be described in more detail below incorporate an
electric motor which is arranged to produce translational movement
of an output member. The actuators to be described may be used as
part of an automatic vehicle speed control system for controlling a
vehicle to run at a desired speed. In such systems, a control
signal is developed depending on any error between actual and
desired speeds for the vehicle, and this control signal energises
the actuator whose output member adjusts the engine power (such as
by adjusting the engine throttle in the case of an internal
combustion engine) so as to bring the vehicle to the desired speed.
However, the actuators to the described are not limited to such
use.
SUMMARY OF THE INVENTION
According to the invention, there is provided an actuator,
comprising a motor having a rotatable output shaft, an output
member mounted for translational movement, and epicyclic gearing
for providing geared reduction of the rotation of the motor shaft
and connecting it to the output member to cause translational
movement thereof, the epicyclic gearing being arranged axially of
the motor shaft.
According to the invention, there is also provided an electric
motor-driven actuator, comprising: an electric motor; a first
epicyclic gear unit having a stationary annulus gear mounted
coaxially of the motor shaft, and a planet cluster comprising a
plurality of planet gears rotatably supported on a planet carrier
and internally meshing with the annulus gear and connected to be
rotated by the motor shaft so as to cause the planet carrier to
rotate; a second epicyclic gear unit comprising a second annulus
gear mounted coaxially of the motor shaft, and a second planet
cluster comprising a plurality of planet gears rotatably supported
on a planet carrier and internally meshing with the second annulus
and connected to be rotated by rotation of the planet carrier of
the first epicyclic unit, clutch means for releasably braking the
annulus of the second epicyclic unit so that, when the second
annulus is braked, rotation of the motor shaft causes rotation of
the second planet carrier and, when the second annulus is not
braked, rotation of the motor shaft results in rotation of the
annulus of the second unit but not in rotation of the planet
carrier thereof; and a coupling connecting the planet carrier of
the second epicyclic unit to cause translational movement of an
actuator output member of the actuator.
DESCRIPTION OF THE DRAWINGS
An electric motor-driven actuator embodying the invention will now
be described, by way of example only, with reference to the
accompanying diagrammatic drawings in which:
FIG. 1 is an exploded view of the actuator;
FIG. 2 is a section showing a modified form of part of the actuator
of FIG. 1;
FIG. 3 is a section showing another modified form of the same part
of the actuator; and
FIG. 4 is a section on the line IV--IV of FIG. 3.
DESCRIPTION OF PREFERRED EMBODIMENTS
The actuator has an electric motor 5 having an output shaft on
which is carried in a pinion 6. This pinion passes through a hole 8
in a base plate 10. Rigid with the base plate 10 is a gear 12
carrying gearing 14. The base plate 10 is rigidly fixed to the
housing of the motor 5 by means of screws 16 (only one shown) which
pass through holes 18.
A ring 20 carrying an annulus gear 22 forms part of a first
epicyclic gear unit 23. Ring 20 sits on the base plate 10 so that
its annulus gear engages the gearing 14 which thus holds the ring
20 stationary. The epicyclic unit 23 is completed by a planet
cluster 24 comprising planet gears 26,28 and 30 which are driven by
the pinion 6, mesh internally with the annulus 22, and are freely
rotatably supported on a planet carrier 32 which is rigid with a
pinion 34.
A second epicyclic unit 35 comprises a ring 36 carrying an annulus
gear 38. The ring 36 is similar in configuration to the ring 20 but
is mounted in the actuator in inverted form as compared with the
ring 20. The facing ends of the rings 20 and 36 carry respective
arrays of teeth 40 and 42 which face each other axially of the
actuator. Each ring 20, 36 has a respective flange 44,46 between
which is mounted a circular spring 36 in the form of an undulating
washer. This spring biases the ring 36 away from the ring 20 so as
to move its face teeth 42 out of engagement with the teeth 40 on
the ring 20. In a manner to be described, however, the ring 36 can
be moved axially, against the action of the spring 48, so as to
bring the teeth 40 and 42 into engagement. It will be apparent that
this locks the rings together so as to prevent rotation of ring
36.
The second epicyclic unit 35 is completed by a planet cluster 50 in
the form of three planet gears 52,54 and 56 which are freely
rotatably supported on a planet carrier 58 and engage the annulus
gear 38 and are themselves engaged by the pinion 34. The planet
carrier 58 carries a coupling 60 having a square hole 62 and lugs
64 which fit into recesses in the planet carrier 58.
The actuator also incorporates an electromagnetic coil mounted
within a coil housing 70 which has a through hole 71 and three arms
72 (only two visible).
A clutch thrust member 74 is slidably mounted around the outside of
the housing 70 with its lower peripheral end sitting on the flange
46 of the ring 36. Slots 76 provide clearance for the arms 72. A
disc 82 of magnetic material, having a through hole, rests on the
uppermost periphery of the clutch thrust member 74. A slot 80
provides clearance for the electrical leads 82 connected to the
coil in the housing 70.
When the actuator is assembled, the coil housing 70 is held at a
fixed distance from the base plate 10 by three hollow cylindrical
spacers 90 (only one shown) which are respectively mounted in
alignment with the three arms 72 of the housing 70 and with holes
92 in the plate 10.
A take-off housing 100 is mounted on top of the magnetic disc 82
and held in a fixed axial position by means of three hollow
cylindrical spacers 102 (only one shown) each of which is
positioned in alignment with a respective one of the arms 72 on the
housing 70 and with a respective integral bore 104 of the housing
100. The housing has a base 106 with a through hole 108, through
which extends a shaft 110 having a squared end which engages the
square hole 62 in the coupling 60. The upper end of the shaft 110
is integral with a disc 112 which carries an integral boss 114. The
boss 114 has a slit 116 by means of which the enlarged head 118 at
the end of a spiral tape 120 may be located in a correspondingly
shaped recess 122, with the tape thus encircling the boss 114. The
other end of the tape 120 is in the form of a tangentially
extending arm 124 having an enlarged head which locates in a keyway
126 in a cable end 128. The cable end 128 has another keyway 130
for receiving the head 132 of a cable 134. The cable extends
outwardly through a boss 136 and a support 138 for an outer casing
140. A spiral spring 150 has ends 152 and 154 which respectively
engage locating points on the inside of the housing 100 and the
underside of the ring 112.
The actuator has an end ring 156 which sits within the open end of
the housing 100 and locates the disc 112.
The assembly is held together by means of three studs 160 (only one
shown), each of which has a screw-threaded upper end 162 receiving
nuts 164 and 166 which hold a clip 168 in position, the three clips
gripping the end ring 156. Each stud 160 passes through a
respective one of the bosses 104, the spacers 102, the arms 72, the
spacers 90 and the holes 92, and is held securely in position by
means of a respective nut 170.
A cover 172 encloses the working parts of the actuator and has a
cable entry 174 for the electrical leads to the motor 5. It may for
example be swaged in position.
In operation, the rings 20 and 36 and the coil within the housing
70 act as an electromagnetic clutch. When the coil is electrically
energised, the resultant magnetic force causes the magnetic disc 82
to be drawn axially towards the coil housing (downwardly as viewed
in FIG. 1) and pushes the clutch thrust member 74 downwardly (this
movement being permitted by the slits 76). The member 74, in moving
downwardly, presses on the flange 46 and drives the ring 36
downwardly so that its teeth 42 engage the teeth 40 on the ring 20.
This movement takes place against the bias of the spring 48.
Engagement of the clutch in this way thus causes the ring 36 to be
held stationary, because the ring 20 is itself held stationary by
engagement of the annulus gearing 22 with the gearing 14.
Energisation of the motor 5, and the consequent rotation of the
pinion 6, will thus rotate the planet gears 26,28 and 30. Since the
annulus 22 is held stationary, the planet carrier 32 will itself
rotate, but at a reduced speed compared with that of the pinion 6.
This rotation of the planet carrier 32 will rotate the pinion 34
correspondingly which drives the planet gears 52,54 and 56. Because
the ring 36 is held stationary by the engaged clutch, the planet
carrier 58 will thus rotate, but at a further reduced speed. This
rotation will be transmitted by the drive coupling 60 to the shaft
110. The resultant rotation of the ring 112 and the boss 114 will
be transmitted to the cable 134, either pulling or pushing on the
cable according to the direction of rotation of the motor 5.
The spring 150 may be arranged to exert its spring bias in either
direction, as desired: that is, it may be arranged to exert a bias
which gives a slight pulling force on the cable 134 or a slight
pushing force.
When the clutch is disengaged, by de-energising the coil within the
coil housing 70, the magnetic force acting on the disc 82 is
removed and the ring 36 moves axially away from the ring 20 under
the action of the spring 48. Ring 36 is thus freely rotatable. The
result of this is that the rotating planet gears 52,54 and 56 now
cause the ring 36 to rotate and transmit no rotation to the planet
carrier 58.
The use of epicyclic gearing provides a simple and compact way of
producing a very substantial reduction in rotational speed (or
angular distance covered) between the output shaft of the motor and
the shaft 110. It also enables the actuator to be constructed with
substantially all its parts arranged symmetrically around its axis.
The epicyclic units 23 and 35 can be substantially identical, thus
simplifying manufacture and production.
Advantageously, a substantial part of the actuator is made of
suitable plastics material. For example, the base plate 10 and the
epicyclic units may all be made of plastics material as may the
coil housing 70, the clutch thrust member 74, the housing 100 and
the cover 172.
When used in a vehicle speed control system, the actuator may be
used to position the throttle of the engine carburettor--to which
it would be connected by the cable 134. The clutch permits
substantially instantaneous release of the drive to the output
shaft 110, allowing the throttle to close under the action of the
spring 150 and of any other spring which may be connected to the
throttle mechanism.
FIGS. 2, 3 and 4 show modified forms which the output end of the
actuator can have, that is, the part of the actuator which converts
the rotary movement into the translational pull on the cable 134.
In certain applications, the arrangement shown in FIG. 1 may
generate insufficient pull on the cable to overcome the drag in its
casing and the bias of the return spring 150. Limitations of space
may prevent the increased pull being obtained by altering the
effective gear ratios of the epicyclic gearing and/or by increasing
the output power of the motor. The latter step could cause undue
heating which might be difficult to dissipate.
The modification shown in FIG. 2 replaces the take-off housing 100
of FIG. 1 and its component parts. In FIG. 2, parts corresponding
to parts in FIG. 1 are correspondingly referenced.
As shown in FIG. 2, a housing 170 is arranged to be bolted on
instead of the housing 100 by studs similar to the studs 160 of
FIG. 1 which enter threaded bores 171. Inside the housing 170 are
shown the housing 70, the clutch thrust member 74 and the disc 82
of FIG. 1.
The housing 170 has a cover 172 which is bored to hold a bearing
174 in which runs the upper end of a shaft 176 corresponding to the
shaft 110 of FIG. 1. This shaft has a squared end which locates in
the square hole 62 in the coupling 60 of FIG. 1. The shaft carries
a pinion 178 which is rigid with it and is in meshing engagement
with a pinion 180 carried on a shaft 182. Shaft 182 is supported at
one end by a bearing 184 running in a wall 186 across the housing
170 and is supported at the other end by a bearing 188 in the top
172. The shaft 182 is rigid with a boss 190 corresponding to the
boss 114 of FIG. 1. The boss 190 carries the spiral tape 120 (of
FIG. 1) which, in similar fashion to that shown in FIG. 1, would be
connected to the cable end 128 of the cable 134, one end of this
tape being fixed to the periphery of the boss 190. The cable and
its casing are not shown in FIG. 2 but the casing would be attached
to a bracket 191.
A return spring corresponding to the return spring 150 of FIG. 1 is
located in the space 192 shown in FIG. 2 and acts on a lug 194 on
the boss 190.
In operation, therefore, rotation of the shaft 176 rotates the boss
190 through the intermediary of the meshing pinions 178 and 180 and
the shaft 182 and thus causes translational movement of the cable
134. The meshing pinion 178 and 180 provide increased mechanical
advantage.
In the arrangement shown in FIGS. 3 and 4, the housing 100 of FIG.
1 is replaced by a housing 200 which is secured in position to the
remainder of the actuator by studs corresponding to the studs 160
of FIG. 1, these studs passing through bores or the like
corresponding to the bores 104 of FIG. 1 but which are not visible
in FIG. 3. The housing 200 has a cover 202 which is held in
position by countersunk screws 204. The cover 202 carries a stud
206 supporting a bearing 208 in the hollow end of a shaft 210.
Shaft 210 corresponds to the shaft 110 of FIG. 1 and has a squared
end which locates in the square hole 62 in the coupling 60 of FIG.
1. The shaft 210 is rigid with a boss 212. This boss corresponds to
the boss 114 of FIG. 1 and can carry a spiral tape corresponding to
the tape 120, one end of this tape being locked to the periphery of
the boss 212 and its other end being connected to the cable 134 in
the same manner as in FIG. 1, the cable passing out through an exit
hole 214.
It will be observed that this construction enables the diameter of
the boss 212 to be significantly less than that of the boss 114 in
FIG. 1, thus achieving the desired increased mechanical
advantage.
In fact, because of the smaller diameter of the boss 212, the use
of a tape corresponding to the tape 120 may not be entirely
satisfactory because of its inability to bend sufficiently.
Instead, therefore, a small ball chain may be wound round the boss
212 with one of its ends locked to the periphery of the boss and
the other fixed to the cable end.
Because the boss 212 is of smaller diameter than the boss 114 of
FIG. 1, a single revolution of the shaft 210 may not produce
sufficient linear movement of the cable and it may therefore be
necessary to permit the shaft 210 to make more than one revolution.
In order to provide a stop defining the total angular movement
permitted to the shaft, a disc 214 is rigidly mounted on the shaft
210 and is provided with a spiral groove 216 as most clearly shown
in FIG. 4. A plate 218 is rigidly fixed in the housing and supports
a pin 220 on which is mounted a swingable link 222. The latter
carries a pin 224 which engages the groove 216. The total permitted
angular movement of the shaft 210 is therefore controlled by the
length of the spiral groove 216.
A return spring corresponding to the spring 150 of FIG. 1 is not
shown in FIG. 3 but may be located within the space 226 so as to
act on a lug 228 on the disc 214.
A seal 230 is provided to prevent ingress of dirt etc.
The arrangement shown in FIGS. 3 and 4 is simpler than that shown
in FIG. 2 and should be less expensive because it involves no
additional gearing and fewer bearings.
* * * * *